1. Field of the Invention
The present invention relates to water-based protective compositions for coating films and preparation processes thereof. Specifically, the present invention is concerned with water-based protective compositions which can be applied onto painted or otherwise coated surfaces of motor vehicles, agricultural machines, construction machines and other machines and equipment for their temporary protection and also with preparation processes thereof.
2. Description of the Prior Art
Large commodities such as motor vehicles are prone to fouling, staining, smear or the like at painted or otherwise coated surfaces by wind and rain, moisture, sunlight, air, iron powder, bird droppings, pollutants in the air such as soot, etc. during the periods until they are delivered to end consumers. To prevent such fouling and maintain their commercial values, it has been the conventional practice to additionally apply a coating-film-protecting agent over coated surfaces of a motor vehicle or the like and to remove the protecting agent shortly before its delivery to a consumer.
The coating-film-protecting agent mentioned above is, as is apparent from its application purpose, required to have durability high enough not to be removed easily by wind, rain, moisture and the like and also to have easy removability permitting easy stripping-off with an organic solvent or water or by hand-wiping whenever its removal is needed.
Conventional coating-film-protecting agents include, for example, wax-solvent dispersions (e.g., Japanese Patent Laid-Open No. 28534/1975), strippable barrier coats (removable when they become no longer needed; for example, Japanese Patent Publication No. 7303/1979), wax-solid powder-solvent dispersions (hand-wiping is feasible; for example, Japanese Patent Laid-Open No. 149188/1976 or 62978/1980), and water-based emulsions (a wax is emulsified and dispersed; for example, Japanese Patent Publication No. 34030/1970). Among these coating-film-protecting agents, drawbacks of those accompanied by evaporation of an organic solvent upon coating and drying and those requiring an organic solvent upon removal, especially, pollution problems, wasting of natural resources, economy and safety are highlighted in recent years.
Interests have hence been concentrated on coating-film-protecting agents of the acrylic polymer emulsion type having the advantages that they are free of evaporation of organic solvent and can be easily removed with alkaline water (Japanese Patent Publication No. 50517/1980, Japanese Patent Laid-Open No. 253673/1987, etc.). These coating-film-protecting agents are also excellent from the standpoint of protective action for the prevention of rusting and damages of metal surfaces.
However, the above-mentioned coating-film-protecting agents of the acrylic polymer emulsion type are not considered to be fully satisfactory in overall properties. Their protecting effects were sometimes insufficient, for example, when a plasticizer or a surface active agent contained in acrylic resins attacked coated surfaces which were supposed to be protected or when the barrier-coated surfaces were exposed to sunlight (ultraviolet rays) under the blazing sun in summer. There has accordingly been a desire for the development of a water-based coating-film-protecting agent which is sufficient in various properties required for coating-film-protecting agents while retaining the excellent performance of coating-film-protecting agents of the acrylic polymer emulsion type.